Atomic charges in molecules defined by molecular real space partition into atomic subspaces.

Area of Science:

• * Computational Chemistry
• * Quantum Chemistry
• * Molecular Modeling

Background:

• * Atomic charge (AC) distribution is fundamental to molecular structure, reactivity, and interactions.
• * Various theoretical models exist, broadly categorized into fuzzy-atom models and those with sharp atomic boundaries.
• * Existing methods include Mulliken, NPA, Hirshfeld, MK, CHELPG, EEM, ABEEM, and APT.

Purpose of the Study:

• * To provide an overview of atomic charge calculation methods.
• * To specifically detail Quantum Chemical Topology (QCT) approaches: Quantum Theory of Atoms in Molecules (QTAIM) and PAEMQCT.
• * To highlight the characteristics and frameworks of QCT-derived ACs.

Main Methods:

• * Review of established population analysis methods (e.g., Mulliken, NPA).
• * Detailed explanation of the Quantum Chemical Topology (QCT) framework.
• * Application of QTAIM and PAEMQCT for atomic partitioning and AC calculation.

Main Results:

• * QCT provides a basis for partitioning molecules into atoms with sharp boundaries.
• * ACs derived from QTAIM correlate well with atomic valence concepts in chemistry.
• * ACs from PAEMQCT show potential utility in modeling molecular interactions.

Conclusions:

• * QCT offers a robust framework for defining atoms within molecules.
• * QTAIM and PAEMQCT provide distinct and valuable approaches to calculating atomic charges.
• * PAEMQCT holds promise for practical applications in simulating intra- and inter-molecular phenomena.